The present invention relates to a chemical-sensitization photoresist composition or, more particularly, to a photoresist composition, which may be of the positive-working type or negative-working type, containing a unique acid-generating agent capable of releasing an acid when exposed to actinic rays. The photoresist composition gives a patterned resist layer having high heat resistance and high resolution with a high photosensitivity of the photoresist composition without being affected by the influences of standing waves so that the patterned resist layer has an excellently orthogonal cross section.
It is a trend in recent years in the manufacturing technology of various electronic devices such as semi-conductor devices involving the process of photolithographic patterning works that so-called chemical-sensitization photoresist compositions are acquiring more and more prevalence by replacing those of the traditional types by virtue of the high sensitivity and high resolving power as compared with conventional photoresist compositions. The chemical-sensitization photoresist composition mentioned above contains a radiation-sensitive acid-generating agent which is a compound capable of releasing an acid when exposed to actinic rays so as to catalyze the solubilizing reaction and crosslinking reaction of the resinous ingredient in the positive- and negative-working photoresist compositions, respectively.
The chemical-sensitization photoresist compositions include two classes of positive-working and negative-working ones depending on the activity of the radiation-released acid either to increase or to decrease, respectively, the solubility of the film-forming resinous ingredient in the composition in an aqueous alkaline solution as a developer. In other words, the chemical-sensitization photoresist composition is positive-working when the film-forming resinous ingredient therein is imparted with an increase in the solubility in the alkaline developer solution and is negative-working when the film-forming resinous ingredient therein is imparted with a decrease in the solubility in the alkaline developer solution.
Accordingly, a positive-working chemical-sensitization photoresist composition usually contains a polyhydroxystyrene and the like of which a part of the hydroxy groups are substituted by solubility-suppressing acid-dissociable protective groups such as tert-butoxycarbonyl and tetrahydropyranyl groups while the film-forming resinous ingredient in the negative-working chemical-sensitization photoresist composition is usually a combination of an acid-crosslinkable melamine resin, urea resin and the like with an alkali-soluble resin such as novolac resins and polyhydroxystyrene resins optionally protected for a part of the hydroxy groups with the solubility-suppressing groups.
It is known that the resinous ingredient mentioned above in the photoresist composition should have a narrow molecular weight distribution expressed by the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn, i.e. Mw:Mn, in order to ensure high resolution of patterning and high heat resistance of the patterned resist layer.
The acid-generating agent heretofore proposed or currently used in chemical-sensitization photoresist compositions includes oximesulfonate compounds as disclosed in Japanese Patent Kokai 1-124848, 2-154266, 2-161444 and 6-67433, of which those oximesulfonate compounds having a cyano group in the molecule are preferred as exemplified by .alpha.-(p-toluenesulfonyloxyimino)benzyl cyanide, .alpha.-(4-chlorobenzenesulfonyloxyimino)benzyl cyanide, .alpha.-(4-nitrobenzenesulfonyloxyimino)benzyl cyanide, .alpha.-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)benzyl cyanide, .alpha.-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide, .alpha.-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide, .alpha.-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide, .alpha.-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide, .alpha.-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide, benzenesulfonyloxyimino-2-thienyl acetonitrile, .alpha.-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide, .alpha.-(p-toluenesulfonyloxyimino)-4-methoxybenzyl cyanide, .alpha.-(4-dodecylbenzenesulfonyloxyimino)-4-methoxybenzyl cyanide, p-toluenesulfonyloxyimino-3-thienyl acetonitrile and the like.
It is noted that each of the above named cyano group-containing oximesulfonate compounds has two aromatic groups in a molecule, one, substituting the .alpha.-carbon atom to which the cyano group --CN is bonded and, the other, forming the sulfonate ester. While the acid released from such a dually aromatic oximesulfonate compound by the irradiation with actinic rays is therefore an aromatic sulfonic acid such as benzenesulfonic acid and p-toluenesulfonic acid, a chemical-sensitization photoresist composition formulated with such an oximesulfonate compound and a resinous ingredient having a narrow molecular weight distribution mentioned above has a defect that the patterning of the resist layer is susceptible to the influences of standing waves so that the cross sectional profile of the patterned resist layer is not exactly orthogonal but has wavy or undulated side lines.